Initial commit: LAN Checker

Network health monitoring script with MQTT reporting for Home Assistant.
- Ping, HTTP, and SNMP checkers
- MQTT Discovery for automatic entity creation
- Configurable check intervals

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

checkers/base.py

@@ -0,0 +1,21 @@
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+from typing import Any
+
+
+@dataclass
+class CheckResult:
+    success: bool
+    message: str
+    response_time: float | None = None
+    details: dict[str, Any] | None = None
+
+
+class BaseChecker(ABC):
+    def __init__(self, name: str, config: dict):
+        self.name = name
+        self.config = config
+
+    @abstractmethod
+    def check(self) -> CheckResult:
+        pass